Tris-(2-hydroxyalkyl)-phosphine oxides

ABSTRACT

TRIS-(2-HYDROXYALKYL)-PHOSPHINE OXIDES OF THE FORMULA   (R-CH(-OH)-CH2)3-P=O   IN WHICH R SIGNIFIES AN ALKYL GROUP HAVING 1 TO 6 CARBON ATOMS AND HAVING 0-6 HALOGEN SUBSTITUENTS ARE PROVIDED. A PROCESS FOR PREPARING THESE PHOSPHINE OXIDES AND THE USE THEREOF AS FLAMEPROOFING AGENTS ARE DISCLOSED.

United States Patent 3,748,363 TRIS-(Z-HYDROXYALKYD-PHOSPHINE OXIDES Ludwig Maier, Zurich, Switzerland, assignor to Monsanto Company, St. Louis, M0.

N0 Drawing. Original application Nov. 18, 1970, Ser. No. 90,787, now Patent No. 3,666,543. Divided and this application Feb. 7, 1972, Ser. No. 224,212

Claims priority, application Switzerland, Nov. 24, 1969,

17,554/69; Aug. 31, 1970, 12,973/70 Int. Cl. C07f 9/50 U.S. Cl. 260606.5 P 6 Claims ABSTRACT OF THE DISCLOSURE Tris- (2-hydroxyalkyl)-phosphine oxides of the formula (ROHOH,)P0

in which R signifies an alkyl group having 1 to 6 carbon atoms and having 0-6 halogen substituents are provided. A process for preparing these phosphine oxides and the use thereof as fiameproofing agents are disclosed.

This is a division of application Ser. No. 90,787 filed Nov. 18, 1970 (now US. 3,666,543).

BACKGROUND OF THE INVENTION with at least twice a molar amount of chlorine at a temperature of from 15 to 50 C. and at a pH in the range of 1 to 7. When the novel phosphine oxides are applied to combustible products the flame resistance thereof is increased.

DETAILED DESCRIPTION The tris-(Z-hydroxyalkyl)-hydroxymethylphosphonium chlorides serving as starting compounds in the present invention may be prepared by reacting tetrakis-(hydroxymethyl)-phosphonium chloride with a corresponding 1,2- alkylene oxide, e.g., a-epihalohydrin, using a molar ratio of 1:3 in aqueous solution at a pH of from about 8 to 9 and a preferred temperature of from about 15 to 30 C. The solution is neutralized and concentrated by evaporation for the isolation of the product. The product may be extracted with, e.g., ethyl alcohol. However, for the preparation of the desired tris-(2-hydroxyalkyl)- phosphine oxide, the aqueous solution after having been at least neutralized, may also directly be treated with chlorine. The chlorine is introduced expediently at room temperature. A higher temperature than about 50 C. is not desirable. The tris-(2-hydroxyalkyl)-phosphine oxides, especially tris-(3-chloro 2 hydroxypropyl)-phosphine oxide and tris-(3 bromo-Z-hydroxypropyl)-phosphine oxide are excellent flameproofing agents for combustible materials like polyesters, polyurethanes, polyamides, polyhydrocarbons, cellulose, cellulose derivatives, paper and wood. The compound may be added to, for example, the spinning dopes or melts to be extruded, or textiles, paper, wood and the like may be impregnated with a Patented July 24, 1973 solution. When compared with phosphine oxides having hydroxymethyl groups such as tris-(hydroxymethyD- phosphine oxide, the compounds of invention possess a greater thermal stability in that they do not release toxic formaldehyde upon heating to the temperature at which tris-(hydroxymethyl)-phosphine oxide releases formaldehyde. Likewise upon stronger heating and comparing at the same higher temperature, no easily volatile and very toxic phosphine is formed. The compounds of this invention also show advantages over the solid tris-(chloromethyl)-phosphine oxide (M.P. 99100 C.), in that they are surprisingly liquid and naturally much less volatile and, moreover, display better solubility in organic solvents. Textile fibers made flameproof with same are less brittle. The halogenated products like tris-(3-halo-2-hydroxypropyl)-phosphine oxide possess the advantages of the formerly used hydroxylated or halogenated trimethylphosphine oxides without their disadvantages, owing to the simultaneous presence of hydroxy groups and halogen atoms in the same molecule.

The novel phosphine oxide compounds further are useful as plasticizers. They can be used instead of well known plasticizers which latter may be replaced totally or partially. Conventional methods can be used to incorporate the compounds into polymers. In general, the amount of phosphine oxide compound added to the base combustible material will range from 0.5 to 20 weight percent. The novel phosphine oxide compounds also are valuable intermediates. The hydrogen atom of the hydroxyl group is exchangeable in the same manner as that of ordinary alcohols. With acid chlorides such as, e.g., acetyl chloride, benzoyl chloride etc., the corresponding ester derivatives of the tertiary phosphine oxides having the formula OICHgC/HCHQ PO in which R" signifies a correspoding organic group, can be obtained employing well known methods. The halogen atom possibly present in the hydroxyalkyl group can be replaced in usual manner. By reacting with an alcohol, phenol or mercaptan in form of their alkali salts or in the presence of a tertiary base such as, e.g., triethylamine, using common methods, however temperatures not higher than about 100 C., the corresponding ether derivatives of the tertiary phosphine oxides: having the formulae R'00H.oHOH.)P0 and RSCHZCHOHZ PO H H )a in which R is derived from the reactant substituting the chlorine atom, can be obtained. In such a halogen exchange it is known that the alcohols, phenols and mercaptans used may also have inert substituents such as, e.g., tertiary amino, acyl, ether, ester groups and halogen atoms. It will be perceived that both the above described reactions possibly may be combined. The resulting compounds showing an ether or thioether group also are valuable plasticizers. The thermally more stable aromatic derivatives are also useful as hydraulic fluids and lubricants. The ester derivatives may find similar usage as the ethers.

The following examples are illustrative of the invention.

EXAMPLE I To a solution containing 33.5 g. (0.0886 mol) of tris-(3- chloro-2-hydroxypropyl)-phosphonium chloride in ml. of water HCl (1:1) was added by drops to reduce the pH of the solution to 1. Then, 13.8 g. of chlorine were led in to the reaction vessel at 20 C. The pH was kept at about 1 by addition of requisite amounts of sodium hydroxide solution. When the introduction of chlorine gas was completed, the solution was neutralized and evaporated to dryness. The residue of the evaporation was dissolved in ethyl alcohol, the precipitated NaCl filtered off, the filtrate concentrated by evaporation, the residue dissolved in water, and the solution passed through a cation exchanger (D'owex 50 Na Upon evaporation the residue was dried at 80 C. in vacuo. Nineteen grams (65.5% yield) of His- (3-chloro-2-hydroxypropyl)-phosphine oxide, yellowish oil were produced.

The resulting product was analyzed by high resolution nuclear magnetic resonance spectroscopy. By this analytical technique the chemical structure of tris-(3-chloro-2- hydroxypropy1)-phosphine oxide was confirmed.

The phosphonium chloride starting compound was obtained as follows:

A solution of 19.0 grams (0. 1 mol) of (HOCH PCl in 10 ml. of water was brought to a pH of 8.3 by addition of 5 N-potassium hydroxide solution, and then 27.7 grams (0.3 mol) of a-epichlorohydrin (1-chloro-2,3- epoxypropane) were added by drops. The temperature was kept at about 20 to 30 C. by cooling with ice and the pH was maintained between 8 and 9 by addition of hydrochloric acid (1:1) as required. After the mixture had been allowed to stand for 18 hours, the solution was concentrated by evaporation; the residue of evaporation dissolved in ethyl alcohol, the separated KCl filtered off and the filtrate completely concentrated and dried at 80 C. in vacuo.

Thirty-seven grains (97.9% yield) of a highly viscous slightly yellowish oil were produced.

The resulting product was analyzed by high resolution nuclear magnetic resonance spectroscopy. By the analytical technique the chemical structure of tris(3-chloro-2- hydroxypropyl)-hydroxymethylphosphonium chloride was confirmed.

EXAMPLE I-I Into a solution of 11.1 grams (0.404 mol) of tris-(2- hydroxypropyl)-hydroxymethylphosphonium chloride in 50 ml. of water were brought 6.3 grams (0.89 mol) of chlorine. The pH of the solution was maintained between 4 to 7. The mixture reacted and the product separated as described in Example I.

Eight and one-half grams (93.6% yield) of tris-(2-hydroxypropyl)-phosphine oxide, a colorless, viscous liquid, were produced.

The resulting product was analyzed by high resolution nuclear magnetic resonance spectroscopy. By this analytical technique the chemical structure of the phosphine oxide was confirmed.

The starting compound was prepared as follows:

From 190.5 grams (1 mol) of tetrakis-(hydroxymethyl)-phosphonium chloride in ml. of water, 53 grams KO'H in 150 m1. of water and 191 grams (3.3 mols) of propylene oxide, there were obtained in a manner similar to that described in the foregoing example 247 grams (90.1%) tris-(2 hydroxypropyl) hydroxymethylphosphonium chloride, a colorless, viscous oil.

I claim:

1. Tris-(2-hydroxyalkyl)-phosphine oxides of the formula in which R signifies an alkyl group having 1 to '6 carbon atoms and 0-6 halogen substituents.

2. Tris-(2-hydroxypropyl)-phosphine oxide. 3. Tris- 3-chloro-2-hydroxypropyl) -phosphine oxide. 4. Process for preparing tris-(2-hydroxyalkyl)-phosphine oxides of the formula (ROHCH,)PO

in which R signifies an alkyl group having 1 to 6 carbon atoms and 0-6 halogen substituents, which comprises treating an aqeuous solution of a tris-(2-hydroxyalkyl)- hydroxymethyl-phosphonium chloride of the formula RCHCH; PCH OH l l 1 in which R has the same significance as above, with at least twice a molar amount of chlorine at a temperature of from 15 to 50 C. and a pH in the range of from 1 to 7.

5. Process for preparing tris-(3-chloro-2-hydroxypropyl)-phosphine oxide comprising treating an aqueous solution of tris-(3-chloro 2 hydroxypropyl) hydro-xymethylphosphonium chloride with at least twice the molar amount of chlorine at a temperature of from 15 to 50 C. and a pH in the range of from 1 to 7.

6. Process for preparing tris-(2-hydroxypropyl)-phosphine oxide comprising treating an aqueous solution of tris-(2-hydroxypropyl)-hydroxymethylphosphonium chloride with at least twice the molar amount of chlorine at a temperature from 15 to 50 C. and a pH in the range of from 1 to 7.

(RCHCEB) P O References Cited UNITED STATES PATENTS 3,404,187 10/1968 Kober et al 260-6065 P 3,452,098 6/1969 Vullo 260606.5 P

WERTEN F. W. BELLAMY, Primary Examiner US. Cl. X.R. 

